Coupler



FIG. 1 is a rear perspective view of a coupler showing my new design;

FIG. 2 is a front perspective view thereof;

FIG. 3 is a elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a left side elevational view thereof; and,

FIG. 8 is a right side elevational view thereof.

The broken line showing of a coupler is included for the purpose of illustrating environmental structure and forms no part of the claimed design. 

The ornamental design for a coupler, as shown and described. 